Current trends in the field of personal documents are in the direction of supplementing the documents that are conventionally used for personal identification with transponders which permit automated contactless reading of the data stored on a chip in the transponder. Such transponders include, in addition to the chip, an antenna coil that allows contactless data access.
Integration or implementation of such transponders in conventional personal documents that contain a plurality of pages of paper accommodated in a document volume makes special demands of the design of the transponder units and/or the so-called transponder inlays, which have the transponder unit on a substrate layer. It is obvious that it is regarded as desirable to interfere with the known format of the identification documents as little as possible through implementation of such a transponder inlay in an identification document. Furthermore, handling of the identification documents, e.g., the pages in such a document, should be influenced as little as possible. On the other hand, the transponder inlays and/or the transponder units arranged on the substrate layers of the transponder inlays are of course subject to special mechanical stresses which naturally derive from the handling of these identification documents.
For the reasons given above, it is therefore assumed that it is especially important to design the transponder inlays intended for implementation in identification documents to be as thin as possible. A reduction in the thickness of the substrate layers used for the transponder inlays is limited already by the thickness of the chip modules if it is assumed that the chip modules are to be accommodated so they are essentially flush with the surface in the transponder inlays.
Designing suitable recesses or window openings in the substrate layers is therefore associated with a significant expense and complexity.